We present a novel approach to computationally model the dynamics of alveolar recruitment/derecruitment (RD), which reproduces the underlying characteristics typically observed in injured lungs. The basic idea is a pressure- and time-dependent variation of the stress-free reference volume in reduced dimensional viscoelastic elements representing the acinar tissue. We choose a variable reference volume triggered by critical opening and closing pressures in a time-dependent manner from a straightforward mechanical point of view. In the case of (partially and progressively) collapsing alveolar structures, the volume available for expansion during breathing reduces and vice versa, eventually enabling consideration of alveolar collapse and reopening in our model. We further introduce a method to patient-specifically determine the underlying critical parameters of the new alveolar RD dynamics when integrated into the tissue elements, referred to as terminal units, of a spatially resolved physics-based lung model that simulates the human respiratory system in an anatomically correct manner. Relevant patient-specific parameters of the terminal units are herein determined based on medical image data and the macromechanical behavior of the lung during artificial ventilation. We test the whole modeling approach for a real-life scenario by applying it to the clinical data of a mechanically ventilated patient. The generated lung model is capable to reproduce clinical measurements such as tidal volume and pleural pressure during various ventilation maneuvers. We conclude that this new model is an important step towards personalized treatment of ARDS patients by considering potentially harmful mechanisms - such as cyclic RD and overdistension - and might help to develop relevant protective ventilation strategies to reduce ventilator-induced lung injury (VILI).

翻译：摘要：我们提出了一种新颖的计算方法，用于模拟肺泡复张/去复张（RD）的动态过程，该方法再现了损伤肺中通常观察到的潜在特征。基本思路是在代表腺泡组织的降维粘弹性单元中，引入压力与时间依赖的应力自由参考体积变化。我们从一个直接的力学角度出发，选择由临界开放和闭合压力以时间依赖方式触发的可变参考体积。在（部分且渐进性）塌陷的肺泡结构中，呼吸期间可用于扩张的体积减少，反之亦然，从而最终使我们的模型能够考虑肺泡塌陷与再开放。我们进一步引入一种方法，在将新肺泡RD动力学整合到组织单元（称为末端单元）中时，患者特异性地确定其关键临界参数。这些末端单元属于一个基于物理的空间解析肺模型，该模型以解剖学正确的方式模拟人体呼吸系统。本文基于医学影像数据和人工通气期间肺的宏观力学行为，确定末端单元的相关患者特异性参数。我们通过将该建模方法应用于机械通气患者的临床数据，测试了其在真实场景中的整体表现。生成的肺模型能够再现临床测量值，如各种通气操作期间的潮气量和胸膜压力。我们得出结论：该新模型通过考虑潜在有害机制（如周期性复张/去复张和过度膨胀），是实现ARDS患者个性化治疗的重要一步，并可能有助于制定相关保护性通气策略，以减少呼吸机诱导的肺损伤（VILI）。